The present invention relates to an input device for a computer system. More specifically, the present invention relates to an input device for providing position information to the computer system based on manipulation of the input device.
A traditional computer input device, such as a mouse, includes a housing with a ball mounted in the housing. The ball is either configured in a traditional manner in which, in the normal work position, the ball engages a work surface and rotates based on the user's movement of the mouse across the work surface. The ball may also be provided as a track ball, which is rotated by digital manipulation from the operator. In either case, position encoders are used to detect rotation of the ball, and to provide positional information indicative of that rotation to the computer. In many instances, the positional information is used to control movement of a visual image (such as a mouse cursor) on the display screen of the computer. This type of input device is referred to as an “absolute” positioning device since movement of the ball correlates to scaled movement of the cursor on the display.
Other input devices that provide absolute positioning include touch-sensitive pads or levers that move in a x-y plane. Touch-sensitive pads are typically fixed in a housing where an operator, using a finger or other pointing device, directs scaled movement of the cursor in a limited range of motion defined by the perimeter of the touch-sensitive pad. Lever operated input devices allow the operator to move an end of the lever in a limited range of motion. Sensors located within the housing track or measure movement of a remote end of the lever from the operator to control cursor movement.
Generally, absolute position devices provide fine resolution and intuitively allow the user to correlate movement of the input device with movement of the cursor. However, long strokes or repeated operation is necessary in order to direct the cursor through large movements on the display or any document that cannot be displayed as a single page.
Other input devices operate under a different principle herein referred to as “relative motion”. One commonly found embodiment of this type is a small joystick that has been placed between keys of a keyboard. An operator pushes the joystick in a direction corresponding to desired movement of the cursor where the magnitude of pressure exerted upon the joystick translates to speed of the cursor in the desired direction. Relative motion input devices are advantageous when large distances must be traversed by the cursor. However, such devices may be cumbersome or awkward to use when fine resolution is necessary.